1. Field of the Invention
The present invention relates to a method and system for scaling the sample rate (e.g., the time or spatial sample rate) of a signal and more particularly, a method and system which may scale a signal sample rate in a transform domain, in the sample domain, or between domains.
2. Description of the Related Art
Compressed signals often need to be scaled in real-time, high-throughput, signal processing systems. For example, a server may provide a wavelet-compressed image at one resolution, but a client personal digital assistant (PDA) may require the image at a different resolution. This PDA resolution is only known at the time of download request, and the scaling must be performed efficiently, either at the server or at the PDA. Thus, scaling must be performed in real time. If the scaling is performed at the PDA, limited processing resources may be available for the operation because of space/power/weight/cost concerns, potentially making the task even more challenging.
Similarly, a production printer (e.g., several hundred impressions per minute, or ipm) may receive a customer job to print in real time, in an encoded print data stream. If a JPEG image (e.g., an image compressed according to a standard developed by the Joint Photographic Experts Group), is embedded in the data stream, the image must be scaled prior to printing. Further, the scaling parameter is only known at the time of decoding of the data stream, therefore, the scaling must be performed in real time.
However, in conventional scaling methods, the scaling matrices are calculated offline and loaded into the signal processing system. Such conventional methods are ineffective when the scaling factors are only known at the time of signal access, and access must be provided in real time. Although having a pre-optimized scaling method is a reasonable expectation for applications where there may be a finite set of supported scaling factors, it does not allow for on-the-fly (e.g., real time) determination of scaling factors. For example, in inkjet printing, the paper may stretch during the printing of each component so that the images for the separate color components should be scaled in real time to compensate for this distortion. Such “real time” scaling factors would require real-time measurement, since they are determined by average job coverage, paper quality and content, ambient conditions, etc.